This invention is in the technical field of coal burners for furnaces and gas turbine engines.
Prior efforts to burn coal in gas turbine engines, such as by use of pulverized coal, or coal in water slurries, have been unsatisfactory due to turbine blade maintenance problems, caused by coal ash particles being carried into the turbine blades, with the hot gases flowing therethrough.
As a result, gas turbine engines, such as are used for electric power generation in combined cycle plants, today burn natural gas, or petroleum distillate fuels, and these fuels are increasingly in short supply, and thus expensive.
As of October 2004, coal cost is about one-fifth of natural gas cost, per unit of energy. Known coal reserves are much greater than known petroleum and natural gas reserves, both nationally, and internationally.
The following United States patents were cited by Examiner Louis Casaregola as relevant to my earlier filed, herein cross referenced, U.S. patent application Ser. No. 11/103,228:                U.S. Pat. No. 2,727,813, Leffer, 1955        U.S. Pat. No. 3,702,516, Luckenbach, 1972        U.S. Pat. No. 4,270,467, Drake, 1981        U.S. Pat. No. 4,331,529, Lambert et al, 1982        
Applicant considers that these cited references differ from his invention, as described herein, in several ways, as follows:
Leffer, U.S. Pat. No. 2,727,813:
Leffer's oxidative destructive distillation zone, 3, has several similarities to my ODD reactor chamber, in that both react bituminous coal with hot, oxygen containing gas, in order to transform bituminous coal into a coke product, and a gas product. Leffer uses small, comminuted coal particles, descending, under gravity, against a counterflowing hot oxygen containing gas, in order to carry out his oxidative destructive distillation process in his reactor chamber, 3. As a result, the descending devolatized coke has first call on the oxygen in the hot gases, and carbon oxides are produced. Leffer's gas product, from reactor chamber, 3, thus contains carbon oxides, unoxidized hydrocarbons, and steam, as described in column 5, lines 40 through 46.
In my ODD reactor chamber, 2, large coal chunks form an essentially fixed coal and coke bed, with intermittent upward motions, at each refuel interval. The hot oxygen containing gas flows through this fixed bed in the same direction as the coal motion. As a result the emerging volatile matter has first call on the oxygen in the hot oxygen containing gases and partially oxidized volatile matter is produced. My gas product from ODD reactor chamber, 2, thus contains partially oxidized, and hence clean burning, volatile matter and inert gases, remaining from the hot, originally oxygen containing, gases.
Leffer seeks to strip the hydrogen from the volatile matter, and deposit the carbon on coke and ash particles, in order to create a synthesis gas product, rich in hydrogen and carbon monoxide. This he accomplished by passing the gaseous product of destructive distillation, from his oxidative destructive distillation reaction, 3, into his gas cracking and reducing reactor, 8, where volatile matter is cracked further to hydrogen gas and carbon, and carbon dioxide is reduced to carbon monoxide. Leffer achieves a different result from his oxidative destructive distillation than I achieve from my ODD reactor chamber.
Luckenbach and Lambert et al; U.S. Pat. Nos. 3,702,516 and 4,331,529
These two inventions describe very similar reactors and reaction processes.
Luckenbach's coker zone, 4, and Lambert's coker reactor, 1, carry out a destructive distillation process, when coal is supplied into them, but not an oxidative destructive distillation reaction, as I do in my ODD reactor chamber, since their fluidizing gas, passing upwardly through these cokers, is free of oxygen molecules. Lambert states that steam is the fluidizing gas in his coker, 1. Luckenbach does not clearly state what fluidizing gas he admits into his coker, 4, at bottom inlet, 5, but it must be free of oxygen molecules as otherwise rapid burning of hydrocarbons and coke would occur in this coker, 4, contrary to Luckenbach's descriptions of the reactions occurring therein.
The reactions in my coke reaction chamber are similar to the reactions in Lambert's first gasifier, 3, and Luckenbach's gasifier, 17, in that the coke supplied thereinto is to be fully oxidized into gaseous products, and solid ashes, by use of reactant gases containing molecular oxygen.
I use large coke chunks in a deep and essentially fixed coke bed in order to produce large ash particles which can be retained by the deep coke bed in my coke reaction chamber, and thus are not carried over into the gas turbine engine blades.
Lambert and Luckenbach use very small coke particles, in a fluidized bed, in order to achieve high reaction rates, and thus use small volume reactor pressure vessels. The inevitable carryover of ash particles is reactified by use of cyclone separators, 23, 36, 38.
In gas turbine engine applications, such use of gas-particle separators, to remove ash particles from combustion gases, has proven unsatisfactory. Several years ago the American railroads jointly carried out a research and development program to use pulverized coal burners, on gas turbine engines, for railroad locomotive power. The gas pressure drop across cyclone separators, required to adequately remove the fly ash particles, unacceptably reduced the efficiency of the gas turbine engine.
Drake, U.S. Pat. No. 4,270,467
Drake uses an essentially conventional cross flow stoker, 6, to burn solid waste fuel materials fully to carbon dioxide reacted gas. I use a counterflow of coke and burner air, in a deep coke fuel bed, with a lengthy carbon dioxide reaction zone, in order to react coke largely to carbon monoxide.